Multifunctionalized magnetic mesoporous silica as an efficient mixed-mode sorbent for extraction of phenoxy carboxylic acid herbicides from water samples followed by liquid chromatography-mass spectrometry in tandem.

In current study, a rapid and sensitive method for simultaneous determination of 8 phenoxy carboxylic acid (PCA) herbicides in environmental water samples was established based on an octyl and amino functionalized magnetic mesoporous silica (mOAS). The mOAS sorbent was fabricated by simple modification of octyl and aminopropyl groups onto the surface of magnetic mesoporous silica. Various techniques were employed to characterize the physical and chemical properties of the mOAS sorbent. The mOAS sorbent showed good extraction capacity and selectivity for PCA herbicides owing to the mixed-mode hydrophobic and ionic exchange interaction mechanisms. Then a one-factor-at-a-time approach was utilized for the optimization of extraction, washing and eluting conditions. Under the optimum conditions, wide linearity ranges with squared correlation coefficients ranging from 0.9888 to 0.9966 were obtained, and the method detection of limits (LODs) were in the range of 0.005-0.02 ng/mL. Furthermore, recoveries ranged from 86.9 to 114.6% with intra- and inter-day relative standard deviation (RSD) of 0.8-11.0% at three concentration levels spiked in blank water sample. Finally, the as-proposed method was successfully applied to extract 8 PCA herbicides in real water samples followed by determination with ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Results showed that the mOAS as adsorbent for magnetic solid phase extraction (MSPE) of acidic herbicides is an efficient alternative with simplicity and rapidity.